"I have great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing," Trump tweeted while on a big foreign trip to Asia.

"Some of those they are harshly treating have been 'milking' their country for years!"

Trump is likely referring to an anti-corruption purge that led to the arrest of 11 Saudi princes and dozens of government ministers. The arrests were widely seen as a move by Crown Prince Mohammed bin Salman to consolidate power.

Trump made his first foreign visit to Saudi Arabia in May. Trump's son-in-law and senior advisor Jared Kushner has also made several trips to Saudi Arabia, including an unpublicized visit in October.

Trump spoke with Saudi King Salman on Saturday, according to a White House readout.

The two leaders discussed fighting the terrorist group ISIS and Iran-backed Houthi rebels in Yemen, as well as Saudi Arabia's arms purchases from the US.

Among the other topics discussed was Saudi Arabia's plans to list state oil company Saudi Aramco on a foreign stock exchange. In a tweet this weekend, Trump publicly pushed for Saudi Arabia to list the company on a US exchange.